My source is the official bits of bio I've found for Medic.

Medic was once a legend in the medical field but later it would all change.

So one day, Medic was assisting a man with his rib lodged in his heart, Medic was very careful, never before did he lose a patient, but soon the man flatlined. Medic was ashamed and left his operating room the same day. Something changed about him just then.

Later, Medic finds himself working on a man with most of his skeleton broken. He wants to do it alone. He goes insane, carefully operating on him. When the patient wakes, he finds his skeleton on a table in front of him. He tilts his head and dies as his brain hits the side of his head. The Medic goes into a frenzy of laughter.

The other doctors and nurses enter the room to find Medic standing on top of the man's corpse. They attempt to catch him but Medic tears them up with his Bonesaw until they are a pile of fresh meat. Once outside, he is arrested and thrown into a mental asylum, where his license is revoked.